District Mail

Steen­bras ground­wa­ter ex­tracted

- South Africa News · Water Security · Ecology · Drought · Social Issues · Society · Natural Disasters · Disasters · Cape Town · Port Elizabeth · Table Mountain · Dan Plato

HELDERBERG – The first ground­wa­ter sup­ply pro­ject of the Ta­ble Moun­tain Group (TMG) Aquifer at the Steen­bras Dam is now op­er­a­tional.

From the first phase of the pro­ject, an ad­di­tional 30 mil­lion litres of wa­ter daily will be con­trib­uted to the City of Cape Town’s wa­ter sys­tem once the pro­ject is fully com­pleted. The pro­ject was launched by mayor Dan Plato and Xanthea Lim­berg, May­oral Com­mit­tee mem­ber for Warer and Waste, last Wed­nes­day (5 Au­gust).

The mile­stone achieve­ment in the im­ple­men­ta­tion of the Cape Town Wa­ter Strat­egy ad­dresses wa­ter sup­ply se­cu­rity and other as­pects of our shared wa­ter fu­ture as ground­wa­ter is a key part of the City’s new wa­ter sup­ply pro­gramme, in a bid to di­ver­sify the mix of wa­ter sources avail­able.

Coun­cil ini­ti­ated drilling op­er­a­tions at Steen­bras dur­ing the drought cri­sis and the TMG Aquifer is now pro­duc­ing its first yield of ground­wa­ter at the Steen­bras Well­field. It is be­lieved to be the largest in the world, with drilling reach­ing a depth of 710 m be­low ground.

“The launch of the first ground­wa­ter from the TMG Aquifer is very ex­cit­ing be­cause this is tes­ta­ment to the City’s com­mit­ment to con­tribut­ing to our long-term wa­ter se­cu­rity,” ex­plained Plato. “This mile­stone needs to be cel­e­brated as it is a step closer to see­ing our wa­ter strat­egy be­come a re­al­ity. The TMG Aquifer is one of the projects listed in the strat­egy, which was launched in Fe­bru­ary.”

The strat­egy aims to make Cape Town more re­silient to drought and other cli­mate shocks, and takes into ac­count the re­la­tion­ships among wa­ter, peo­ple, the economy and the en­vi­ron­ment, he added.

The TMG Aquifer is a ge­o­log­i­cal for­ma­tion that ex­tends from Nieu­woudtville to Cape Agul­has and Port El­iz­a­beth. It is iden­ti­fied as a sig­nif­i­cant source of ground­wa­ter stor­age in the Western Cape. There are cur­rently eight com­pleted pro­duc­tion bore­holes, yield­ing al­most 20 mil­lion litres per day.

Drilling of a fur­ther four is un­der­way, which will even­tu­ally in­crease the yield to 30 mil­lion litres per day.

“To put this into con­text, 30 mil­lion litres per day is the equiv­a­lent of a daily wa­ter sup­ply for around 200 000 peo­ple at cur­rent con­sump­tion lev­els of 125 litres of wa­ter per per­son, per day,” Lim­berg re­lated.

“Al­ter­na­tively, this would rep­re­sent 16 days’ worth of wa­ter for the whole city, for every year of op­er­a­tion. Although there isn’t cur­rently an ur­gent threat to our im­me­di­ate wa­ter se­cu­rity – pro­vided cur­rent re­stric­tions are ad­hered to – we are still en­cour­ag­ing res­i­dents not to for­get the very valu­able lessons learnt about the fi­nite na­ture of wa­ter, our most pre­cious re­source.”

The Steen­bras Well­field was cho­sen due to favourable hy­dro­ge­o­log­i­cal con­di­tions giv­ing rise to a po­ten­tially high ground­wa­ter yield, Lim­berg ex­plained, with the ben­e­fit of it be­ing in close prox­im­ity to the Steen­bras Dam. “This is ideal as the ground­wa­ter can be pumped di­rectly into the dam and treated at the Faure wa­ter treat­ment works to drink­ing-wa­ter stan­dard.”

A key high­light in this pro­ject is the en­vi­ron­men­tal mit­i­ga­tion and con­trols ad­min­is­tered to en­sure the pro­tec­tion of the Steen­bras Na­ture Re­serve, which falls within the Ko­gel­berg Bio­sphere Re­serve.

These mea­sures in­clude the search and res­cue of pro­tected veg­e­ta­tion, top soil man­age­ment, re-us­ing on-site ma­te­rial to pre­vent changes to ground con­di­tions, match­ing his­tor­i­cal ground­wa­ter and sur­face wa­ter move­ment across trenches, in­stalling power lines un­der­ground to al­low for veld fire pre­ven­ta­tive man­age­ment and re­duc­ing the vis­ual im­pact of py­lons, span­ning pipe­lines across rivers in­stead of trench­ing through them as well as re­ha­bil­i­tat­ing dis­turbed ar­eas after con­struc­tion.

Due to the en­vi­ron­men­tal sen­si­tiv­ity of the area and the risk of dam­age by nat­u­ral fire cy­cles in fyn­bos, medium-volt­age power ca­bles and fiberop­tic ca­bles were buried in the same trenches as the pipe­lines.

The fiberop­tic ca­ble net­work feeds all data from the re­spec­tive bore-holes to a cen­tralised Su­per­vi­sory Con­trol and Data Ac­qui­si­tion point (Scada), which al­lows the well­field to be con­trolled and op­er­ated through an au­to­mated sys­tem.

“In­va­sive alien veg­e­ta­tion is be­ing re­moved from the re­serve’s catch­ment area, in an ef­fort to max­imise the rain­wa­ter sur­face run-off yield into the dam,” Lim­berg re­lated. “Pine and bluegum trees are be­ing sys­tem­at­i­cally re­moved and the land is care­fully re­ha­bil­i­tated with in­dige­nous veg­e­ta­tion.

Alien veg­e­ta­tion clear­ance and other short-term projects, are also pro­vid­ing lo­cal work op­por­tu­ni­ties through the Ex­panded Pub­lic Works Pro­gramme.”

The na­tional de­part­ments of Hu­man Settlement­s and Wa­ter and San­i­ta­tion is the cus­to­dian of ground­wa­ter in SA, and has is­sued the City with a wa­ter-use li­cence to ex­tract wa­ter and con­struct in­fra­struc­ture for the pro­ject. To­tal li­censed volume for Phase 1 of the pro­ject is 33 mil­lion litres per day, with an ad­di­tional 15 mil­lion ex­pected from the Nuwe­berg Well­field, now in ex­ploratory drilling phase. So the Steen­bras Well­field forms part of the Western Cape Wa­ter Sup­ply Sys­tem, and was es­tab­lished in col­lab­o­ra­tion with the na­tional De­part­ment of

Wa­ter and San­i­ta­tion.

 ?? Photo: City of Cape Town ?? Clive Jus­tus, chair­per­son of the City’s Wa­ter and Waste Port­fo­lio Com­mit­tee, and Cape Town Mayor Dan Plato launch the Steen­bras Well­field of the Ta­ble Moun­tain Group Aquifer last week.
Photo: City of Cape Town Clive Jus­tus, chair­per­son of the City’s Wa­ter and Waste Port­fo­lio Com­mit­tee, and Cape Town Mayor Dan Plato launch the Steen­bras Well­field of the Ta­ble Moun­tain Group Aquifer last week.

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